Patent GB-1296801-A (GB)
Inventor: DAL MONTE G
IPC: H04Q11/06
Filed: 1971-04-19
Abstract: 1296801 Automatic exchange equipment SOC ITALIANA TELECOMUNICAZIONI SIEMENS SpA 19 April 1971 [10 Feb 1970] 22232/71 Heading H4K An intermediate exchange transmits information in PCM form between incoming and outgoing channels through successive stores of which the first and the last stores are associated directly with the incoming and outgoing channels and of the intermediate stores at least one is capable of non-destructive reading. The transfer of information is regulated by an exchange frequency higher than any associated PCM channel frequency and the period of this frequency is divided into subperiods whose duration is such as to occur complete at least once in a time slot of an associated PCM channel so that the reading of information into the first store and the writing of the information from the last store is commanded by the subperiod. In the timing diagram shown, the exchange frequency Rc is divided into unequal subperiods a, b of which subperiod a occurs in all incoming PCM-E and outgoing PCM-U channel time slots. Four storage areas are provided M1-M4 and the stores M2 and M3 are interconnected at Vc by a space switch CS which provides the required connections between incoming and out. going PCM channels. The store M2 can be non- destructively read and the frequencies of the incoming and outgoing channels differ. The store M1 has two cells each capable of storing the 8 bits of information present in each time slot of the incoming channel and these are filled alternately. The stored information is transferred to store M2 during subperiod a as long as the respective cell is full, thus the information stored during slot 6 cannot be read until the subperiod a in slot 7. The information in store M2 is then transferred, in accordance with the connections VC, to store M3 during subperiod b so that there is no risk of store M2 being empty when interrogated. This information is then stored in either of cells C, D associated with store M4 during subperiod a so that it is ready for transmission into the respective time slot of the outgoing PCM channel. The exchange may be modified and one of the intermediate stores M2 or M3 eliminated by ensuring that both subperiods a and b will occur at least once during every incoming or outgoing time slot. If the periods a, b can be made to have equal duration, Fig. 7 (not shown), or subperiod a can be divided into six equal parts so that a1 and b are the operative subperiods which enables store M2 to be eliminated, Fig. 6 (not shown), and store M3 can be non-destructively read. Alternatively store M3 can be eliminated by subdividing period b into six parts and making a and b6 the operative subperiods, Fig. 5 (not shown). In the actual layout of the exchange, as shown in Fig. 11, the store M2 is connected through a space switch CS which provides the interconnection between the respective input and output channels and a time switch CT which gates the information from store M2 to store M3 at the correct time as defined by subperiod b. Similar layouts are used when one of the stores M2, M3 is omitted and subperiods a1, b6 are used. Figs. 12 and 13 (not shown). In a further modification, Fig. 15 (not shown), a single switch is used which provides both for the selection of channel interconnection and the sequential transfer of information during subperiod b. Similarly the layouts shown in Figs. 12 and 13 can be modified. The exchange is stated to be controlled by a central processor and channel 16 is arranged to be the data channel. During this 16th time slot a connection is made direct to the processor for input or output of control information.